Tolerance and Metabolization of High-Concentration Heavy Crude Oil High-Concentration Heavy Crude Oil by Bacillus subtilis

In this comprehensive study, we investigated the degradation capacity and tolerance of the bacterial strain <i>Bacillus subtilis</i> in culture media with high concentrations of heavy crude oil (HCO) as the sole carbon source. Using a meticulously designed experimental approach conducted at room temperature (25 °C), we systematically examined various culture media with HCO concentrations of 20%, 35%, and 50% <i>v</i>/<i>v</i> over a 10-week period. The results revealed the microorganism's remarkable resistance to these HCO concentrations. Biotransformation capacity was confirmed by quantifying CO₂ production via gas chromatography, showing substantial bioconversion with a 42% increase in CO₂ production. Additionally, changes in surface tension were monitored using the Du Noüy ring method, showing a reduction in the aqueous phase tension from 72.3 to 47.43 mN/m. At the end of the bioconversion period, all treated samples exhibited visible emulsification, indicative of biosurfactant production. This phenomenon was consistent with the observed decrease in surface tension, providing further evidence of biosurfactant-mediated mechanisms. These findings highlight the immense biotechnological potential of <i>B. subtilis</i> to address HCO-related challenges, offering promising prospects for crude oil bioremediation and bioupgrading.